question about NuArc 26-1ks presets *blinking light* at end of exposure

Hey all,

Sometimes (not all the time) after an exposure the red light is blinking. Here's the process:
set units of light on E1 preset
turn on vacuum
start the exposure and exit the room
when I return after the exposure is over the red light next to E1 (or E2 if I've used that as my preset) is blinking